1. Field of Invention
The invention relates to a navigation system and a memory medium that improve a method of determining a guidance terminating point when a road proximate to a destination is determined as a non-guidance target road due to restriction and the like.
2. Description of Related Art
According to a previous navigation system, road data are separately stored for route guidance, and display. The road data for route guidance are used for route search and route guidance. The road data for display are used for displaying a map. Route guidance is executed by distinguishing guidance target roads from non-guidance target roads such as small streets or roads with other restrictions associated therewith. The data for route guidance are stored with accompanying information on traffic restrictions (no left turn, no right turn, no access, etc.) for each road section, and with cost data for recommended route search in view of distance and time, etc. However, data of non-guidance target roads, such as walkways or private roads, are not included in the road data for route guidance since they have sections where traffic restrictions are not checked. If restricted roads exist around a starting point or a destination, a recommended route is provided after a search whereby only roads the vehicle can access are displayed as the path to the desired destination. Alternatively roads with access restriction may be recognized and displayed, perhaps as roads to avoid.
Thus, if a last arrival point (a destination) is connected to a small street that is not previously included in the road data for route guidance, lines are perpendicularly drawn down from the destination to guidance target roads and a point at which the shortest perpendicular line comes into contact with the guidance target road is determined as a guidance terminating point.
An example shown in FIG. 11, if a point P1 on a walk way (W) from a guidance target road (R1) is the desired destination, a line drawn from the destination to contact perpendicularly guidance target road (R2) is the shortest perpendicular line. Therefore, this point P2 is determined as a guidance terminating point P2. In this method, however, guidance is eventually completed using the road (R2) that is not connected to the destination. In this case, for example, if a river runs between the guidance target road (R2) and the destination and there is no bridge near to connect the two, or the like, it is difficult for one to arrive at the destination from the guidance terminating point.
The invention addresses the above problem by executing guidance accurately when a destination connected to a non-guidance target road such as a small street is determined.
A navigation system according to the invention comprises a present position detecting means, an input means for inputting information necessary for searching a route or a destination, a report means for reporting route guidance information, an information memory means for storing data necessary for route search, a route search means for searching a route to a destination on the basis of information input by said input means and data stored in the information memory means, a judgment means for judging whether a road connected to a destination on the searched route is a guidance or a non-guidance target road, and a control means for setting a guidance terminating point on the basis of the result of said judgment means. Further, the navigation system according to the invention provides that the judgment means determines a connecting point between a guidance target road and a non-guidance target road, or the last intersection of the guidance target road to the non-guidance target road, or a road end point of the non-guidance target road closest to the destination side as a guidance terminating point. The navigation system according to the invention, provides guidance information around the destination when the position approaches within a predetermined distance from the destination or the guidance terminating point. Further, the navigation system according to the invention performs even when the non-guidance target road is a street with traffic restrictions. A memory medium according to the invention is also provided wherein a program is stored for detecting a vehicle present position, for searching for a route to a destination on the basis of input information and stored data, for judging whether a road connecting to the destination on the searched route is a guidance or a non-guidance target road, and for determining a guidance terminating point on the basis of the result of the judgment.
According to the invention, one can reach a destination by determining a connection point between a guidance target road and a non-guidance target road even when route guidance is terminated on the guidance target road.